Using advanced spectrum sharing, basic voice services can live on while broadband speeds increase

In the hunt for more spectrum to speed up mobile networks, Vodafone and Huawei Technologies have successfully tested a technology that lets LTE and GSM share the same frequencies.

The speed of future mobile networks will depend on the amount of spectrum mobile operators can get their hands on. The more they get, the wider the roads they can build.

One thing they can do to get more space is to reuse frequencies that are currently used for older technologies such as GSM and 3G. But that isn't as easy as sounds, as operators still have a lot of voice and messaging traffic in those older networks. That traffic isn't going away for a long time, irrespective of the level of competition from Internet-based services.

However, using a technology called GL DSS (GSM-LTE Dynamic Spectrum Sharing) Vodafone and Huawei have shown a way to allow GSM and LTE to coexist.

In a traditional mobile network, operators allocate each technology an exclusive set of frequencies. For example, many operators, including Vodafone, currently hold 20MHz of spectrum at 1.8GHz, of which 10MHz is used for LTE and the rest for GSM traffic.

GL DSS lets Huawei's SRC (Single Radio Controller) give GSM a higher priority during periods of heavy traffic, ensuring that voice calls get though unharmed. But the SRC can also provide more room for LTE when users aren't making calls, allowing for better throughput, the vendor said on Tuesday.

This trial verified the technology's performance in Vodafone Spain's commercial network, with LTE capacity gains of up to 50 percent, according to Huawei. That equals another 32.5Mbps of bandwidth, on paper. Smartphones and other devices with a cellular connection don't have to be upgraded for the technology to work.

"What we see now is that GSM and 3G will live much longer than anyone expected. This could be one of the things you as a carrier do to increase sustainability and scalability," said Sylvain Fabre, research director at Gartner.

Huawei and Vodafone didn't say when they expect GL DSS will become available to users.